Muffler recommendations 1965 barracuda 273 original exhaust manifolds.

It's your car, but it's been proven many times that small cube engines, as well as inline engines benefit more from a good, free flowing single exhaust. I would do something like a 2" wye into a single 3" mandrel bent pipe to the bumper with something like one of the Dynomax Ultra Flow welded mufflers. You can look at the data on their web site and see some of those actually outflow an open pipe. Don't ask me how, it's alien technology. I used one on Vixen and I slam believe it.